全文获取类型
收费全文 | 8890篇 |
免费 | 1261篇 |
国内免费 | 1193篇 |
专业分类
测绘学 | 611篇 |
大气科学 | 1258篇 |
地球物理 | 2800篇 |
地质学 | 4026篇 |
海洋学 | 887篇 |
天文学 | 545篇 |
综合类 | 547篇 |
自然地理 | 670篇 |
出版年
2024年 | 28篇 |
2023年 | 109篇 |
2022年 | 229篇 |
2021年 | 269篇 |
2020年 | 254篇 |
2019年 | 285篇 |
2018年 | 681篇 |
2017年 | 606篇 |
2016年 | 484篇 |
2015年 | 378篇 |
2014年 | 347篇 |
2013年 | 335篇 |
2012年 | 915篇 |
2011年 | 662篇 |
2010年 | 341篇 |
2009年 | 317篇 |
2008年 | 317篇 |
2007年 | 270篇 |
2006年 | 269篇 |
2005年 | 958篇 |
2004年 | 971篇 |
2003年 | 725篇 |
2002年 | 270篇 |
2001年 | 157篇 |
2000年 | 137篇 |
1999年 | 143篇 |
1998年 | 126篇 |
1997年 | 112篇 |
1996年 | 124篇 |
1995年 | 74篇 |
1994年 | 63篇 |
1993年 | 71篇 |
1992年 | 60篇 |
1991年 | 60篇 |
1990年 | 43篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1965年 | 3篇 |
1958年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
91.
92.
93.
地壳由半无限大的基岩上一层厚度为H^-的表土层组成,入射地震波为垂直的SH波,产生水平地面运动。当浅源大地震发生时,在极震区以外行波传播产生地面运动将使地壳介质有非线性的有限弹性变形。用小参数摄动法使非线性控制方程为线性化的小参数各阶控制方程,得出头两阶线性控制方程的解析解。 相似文献
94.
95.
Based on remote sensing information sources including B/W aerial photos of 1983, pseudo-color aerial photos of 1992 and JERS-1/OPS VNIR image of 1996, vegetation types of Yingbazha, in the middle reaches of the Tarim River Basin in Xinjiang, China are mapped using ARC/INFO and related software. The changes in vegetation areas and distribution conditions are analyzed. As a result of natural and human influences, vegetation changes have temporal and spatial characteristics. According to the principles of landscape ecology and geographical information science, the landscape changes are indicated. Moreover, the remote sensing and GIS techniques are integrated to study vegetation and its landscape. 相似文献
96.
Zili Fan Xuncheng Xia Yuling Shen Kurban Alishir Ranghui Wang Shengyu Li Yingjun Ma 《中国科学D辑(英文版)》2002,45(1):102-108
Because of the human exploitation and utilization of water resources in the Tarim Basin, the water resources consumption has changed from mainly natural ecosystem to artificial oasis ecosystem, and the environment has changed correspondingly. The basic changes are: desertification and oasis development coexist, both “the human being advance and the desert retreat” and “the desert advance and the human being retreat” coexist, but the latter is dominant. In the upper reaches, water volume drawing to irrigated agricultural areas has increased, artificial oases have been enlarging and moving from the deltas in the lower reaches of many rivers to the piedmont plains. In the middle and lower reaches of the Tarim River, the stream flow has decreased, old oases have declined, natural vegetations have been degenerating, desertification has been enlarging, and the environment has deteriorated. The transition regions, which consist of forestlands, grasslands and waters between the desert and the oases, have been decreasing continuously, their shelter function to the oases has been weakened, and the desert is threatening the oases seriously. 相似文献
97.
Che Yong-tai Yu Jin-zi Zhang Shu-liang Fan Xue-fang Guo Jun-jie Zhang Tian-yuan Yang Jin-lan 《地震学报(英文版)》2002,15(2):226-233
A lot of slow fluctuations of water level have been observed in the original recording maps of subsurface fluid in Well Shuozhou,
Shanxi Province. Some typical recording maps of the “precursors” are introduced in the paper and the features of the “precursors”
recorded by the well are analyzed. The results show that 38% strong earthquakes possess this kind of record, which has a fluctuation
period arranging from several to tens of minutes and appear mostly two days before the earthquakes. Moreover, the mechanism,
transmission and responding conditions of well water level are discussed, as well as the scientific meaning and practical
value of the “precursor” of the well water level in earthquake predictions.
Foundation item: State Natural Science Foundation of China (19973011). 相似文献
98.
Early Yanshanian post-orogenic granitoids in the Nanling region
Petrological constraints and geodynamic settings 总被引:1,自引:0,他引:1
Petrological constraints and geodynamic settings 总被引:1,自引:0,他引:1
Early Yanshanian magmatic suites predominate absolutely in the Nanling granite belt. They consist mainly of monzogranite and K-feldspar granite. There occur associations of early Yanshanian A-type granitoids (176 Ma-178 Ma) and bimodal volcanic rocks (158 Ma-179 Ma) in southern Jiangxi and southwestern Fujian in the eastern sector of the granite belt and early Yanshanian basalts (177 Ma-178 Ma) in southern Hunan in the central sector of the belt. Both the acid end-member rhyolite in the bimodal volcanic rock association and A-type granitoids in southern Jiangxi have the geochemical characteristics of intraplate granitic rocks and the basic end-member basalt of the association is intraplate tholeiite, while the basaltic rocks in southern Hunan include not only intraplate tholeiite but also intraplate alkali basalt. Therefore the early Yanshanian magmatic suites in the Nanling region are undoubtedly typical post-orogenic rock associations. Post-orogenic suites mark the end of a post-collision or late orogenic event and the initiation of Pangaea break-up, indicating that a new orogenic Wilson cycle is about to start. Therefore it may be considered that the early Yanshanian geodynamic settings in the Nanling region should be related to post-orogenic continental break-up after the Indosinian orogeny and the break-up did not begin in the Cretaceous. 相似文献
99.
新时期我国区域经济地理学发展问题初探 总被引:4,自引:0,他引:4
我国新时期的区域经济地理学在取得全面发展的同时,在理论体系,研究方法和实践领域等方面还需要进一步的发展,文章根据学习和实践区域经济地理学的体会,初步提出基础理论和应用理论,思维方法和技术方法等方面发展见解,并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域,最后提出我国区域经济地理学科发展的建议。 相似文献
100.